Thermo-solvatochromism of merocyanine polarity probes - What are the consequences of increasing probe lipophilicity through annelation?

The question raised in the title has been answered by comparing the solvatochromism of two series of polarity probes, the lipophilicities of which were increased either by increasing the length of an alkyl group (R) attached to a fixed pyridine-based structure or through annelation (i.e., by fusing benzene rings onto a central pyridine-based structure). The following novel solvatochromic probes were synthesized: 2,6-dibromo-4-[(E)-2-(1-methylquinolinium-4-yl)ethenyl]-phenolate (MeQMBr(2)) and 2,6-dibromo-4-[(E)-2-(1-methyl-acridinium-4- yl) ethenyl)]phenolate (MeAMBr(2) The solvatochromic behavior of these probes, along with that of 2,6dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl]phenol-ate(MePMBr(2)) was analyzed in terms of increasing probe lipophilicity, through annelation. Values of the empirical solvent polarity scale [E(T)(MePMBr(2))] in kcalmol(-1) correlated linearly with ET(30), the corresponding values for the extensively employed probe 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (RB). On the other hand, the nonlinear correlations of ET(MeQMBr(2)) or ET(MeAMBr(2)) with E(T)(30) are described by second-order polynomials. Possible reasons for this behavior include: i) self-aggregation of the probe, ii) photoinduced cis/trans isomerization of the dye, and iii) probe structure- and solvent-dependent contributions of the quinonoid and zwitterionic limiting formulas to the ground and excited states of the probe. We show that mechanisms (i) and (ii) are not operative under the experimental conditions employed; experimental evidence (NMR) and theoretical calculations are presented to support the conjecture that the length of the central ethenylic bond in the dye increases in the order MeAMBr(2) > MeQMBr(2) > MePMBr(2), That is, the contribution of the zwitterionic limiting formula predominates for the latter probe, as is also the case for RB, this being the reason for the observed linear correlation between the ET(MePMBr2) and the ET(30) scales. The effect of increasing probe lipophilicity on solvatochromic behavior therefore depends on the strategy employed. Increasing the length of R affects solvatochromism much less than annelation, because the former structural change hardly perturbs the energy of the intramolecular charge-transfer transition responsible for solvatochromism. The thermo-solvatochromic behavior (effect of temperature on solvatochromism) of the three probes was studied in mixtures of water with propanol and/or with DMSO. The solvation model used explicitly considers the presence of three ""species"" in the system: bulk solution and probe solvation shell [namely, water (W), organic solvent (Solv)], and solvent-water hydrogen-bonded aggregate (Solv-W). For aqueous propanol, the probe is efficiently solvated by Solv-W; the strong interaction of DMSO with W drastically decreases the efficiency of Solv-W in solvating the probe, relative to its precursor solvents. Temperature increases resulted in desolvation of the probes, due to the concomitant reduction in the structured characters of the components of the binary mixtures.

Fluorescent probes with malononitrile side group in methyl methacrylate copolymers

Fluorescent probes derivated from auramine, 1-aminopyrene, and 9-aminoacridine containing a malononitrile group are copolymerized with methyl methacrylate. These new fluorescent polymeric materials are studied in solution of different solvents by steady-state and time-resolved emission techniques. Their spectroscopic properties and excited state dynamics are driven by charge transfer from the aromatic group to the electron withdrawing CN groups, and this factor is responsible for the non-exponential emission decay behavior. (c) 2008 Elsevier B.V. All rights reserved.

On the interaction of bovine serum albumin with ionic surfactants: Temperature induced EPR changes of a maleimide nitroxide reflect local protein dynamics and probe solvent accessibility

The interaction of bovine serum albumin (BSA) with the ionic surfactants sodium dodecylsulfate (SDS, anionic), cetyltrimethylammonium chloride (CTAC, cationic) and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS, zwitterionic) was studied by electron paramagnetic resonance (EPR) spectroscopy of spin label covalently bound to the single free thiol group of the protein. EPR spectra simulation allows to monitor the protein dynamics at the labeling site and to estimate the changes in standard Gibbs free energy, enthalpy and entropy for transferring the nitroxide side chain from the more motionally restricted to the less restricted component. Whereas SDS and CTAC showed similar increases in the dynamics of the protein backbone for all measured concentrations. HPS presented a smaller effect at concentrations above 1.5 mM. At 10 mM of surfactants and 0.15 mM BSA, the standard Gibbs free energy change was consistent with protein backbone conformations more expanded and exposed to the solvent as compared to the native protein, but with a less pronounced effect for HPS. In the presence of the surfactants, the enthalpy change, related to the energy required to dissociate the nitroxide side chain from the protein, was greater, suggesting a lower water activity. The nitroxide side chain also detected a higher viscosity environment in the vicinity of the paramagnetic probe induced by the addition of the surfactants. The results suggest that the surfactant-BSA interaction, at higher surfactant concentration, is affected by the affinities of the surfactant to its own micelles and micelle-like aggregates. Complementary DLS data suggests that the temperature induced changes monitored by the nitroxide probe reflects local changes in the vicinity of the single thiol group of Cys-34 BSA residue. (C) 2011 Elsevier B.V. All rights reserved.

On the interaction of bovine serum albumin with ionic surfactants: Temperature induced EPR changes of a maleimide nitroxide reflect local protein dynamics and probe solvent accessibility

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fluorescent amplified fragment length polymorphism genotyping of human and animal Staphylococcus aureus isolates from dairy farms with manual milking

Fluorescence amplified fragment length polymorphism (fAFLP) was used to assess the genetic relatedness of 40 Staphylococcus aureus strains isolated from human and animal skin samples in seven dairy farms with manual milking. S. aureus was isolated from 11 out of 30 (36%) human skin samples and from 29 out of 100 (29%) teat skin samples from apparently healthy cows. Genomic DNA from each isolate was double-digested with EcoRI and MseI and complementary oligonucleotide adaptors were ligated to the restriction fragments. Pre-selective and selective, amplification reactions were performed, the amplified fragments were separated by electrophoresis in an ABI377 sequencer and analysed using GeneScan 3.1 and Genotyper 2.5. Three single isolates (a-c), a predominant cluster with 35 isolates (d) and another cluster with two isolates (e) were identified. Both clusters d and e included human and animal isolates genetically related, because the profiles had 90-100% homology. Since no cluster was comprised uniquely of human or animal isolates and given the close genetic relatedness among human and animal samples in the farms, the present findings support the. hypothesis that dairy workers can spread S. aureus through manual milking. (C) 2005 Elsevier B.V. All rights reserved.

Effects of discontinuous Percoll gradient centrifugation on the quality of bovine spermatozoa evaluated with computer-assisted semen analysis and fluorescent probes association

The objective of this study was to evaluate the quality of bovine frozen-thawed sperm cells after Percoll gradient centrifugation. Frozen semen doses were obtained from six bulls of different breeds, including three taurine and three Zebu animals. Four ejaculates per bull were evaluated before and after discontinuous Percoll gradient centrifugation. Sperm motility was assessed by computer-assisted semen analysis and the integrity of the plasma and acrosomal membranes, as well as mitochondrial function, were evaluated using a combination of fluorescent probes propidium iodide, fluorescein isothiocyanate-conjugated Pisum sativum agglutinin and 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide. The procedure of Percoll gradient centrifugation increased the percentage of total and progressive sperm motility, beat frequency, rectilinear motility, linearity and rapidly moving cells. In addition, the percentage of cells with intact plasma membrane and mitochondrial membrane potential was increased in post-centrifugation samples. However, the percentage of sperm cells with intact acrosomal membrane was markedly reduced. The method used selected the motile cells with intact plasma membrane and higher mitochondrial functionality in frozen-thawed bull semen, but processing, centrifugation and/or the Percoll medium caused damage to the acrosomal membrane.

High power factor dimmable electronic ballast for multiple tubular fluorescent lamps

This paper presents a dimmable electronic ballast designed for multiple fluorescent lamps applications. A ZCS-PWM Boost rectifier and a classical resonant Full-Bridge inverter compose this new electronic ballast, providing conditions for the obtaining of high input power-factor, and soft-switching processes for all semiconductor devices employed in the structure. The instantaneous average input current control technique is employed in the Boost rectifier. Concerning the Full-Bridge inverter, it is controlled by the imposition of phase-shift in the current processed through the sets of resonant filters + lamps, according to an adaptation in a specially designed control IC, called IR2159. Experimental results are presented in order to validate the analyses developed in this paper.

A new model for tubular fluorescent lamps operated at high frequencies for dimmable applications

This paper presents a new static model for tubular fluorescent lamps (T12 bulb) operated at high frequencies. The main goal of this paper is to investigate the effects of ambient temperature and nominal switching frequency of operation in the static characteristics of tubular fluorescent lamps. The methodology for obtaining the model is based on several two-dimensional mathematical regressions, used to provide the behavior of the fluorescent lamp according to different independent variables, namely: power processed through the lamp and ambient temperature. In addition, the proposed model can be easily converted to a lamp equivalent resistance model, which can be useful for ballast designers. Finally, the curves obtained using the new model are compared to the correspondent experimental data, in order to verify the accuracy of the proposed methodology.

Setting the preheating and steady-state operation of electronic ballasts, considering electrodes of hot-cathode fluorescent lamps

This paper presents a new methodology for the adjustment of the preheating process and steady-state operation of electronic ballasts intended for hot-cathode fluorescent lamps. The classical series-resonant parallel-loaded half-bridge inverter is the power stage analyzed in this paper. In addition, the preheating process is based on the imposition of a constant rms current through the electrodes, in order to provide a proper value of the R-h/R-c ratio before the lamp start. According to the proposed methodology, it is possible to set suitable operating points for, the electronic ballast, considering optimal conditions for the lamps electrodes. Therefore, the proposed methodology for setting the preheating and steady-state operation is a complete platform to the design of electronic ballasts for hot-cathode fluorescent lamps.

Automatic dimming multi-lamp fluorescent management system with active input power factor corrector stage

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of refrigeration systems upon frozen bull sperm viability assessed by computer-assisted sperm analysis and fluorescent probes

Sperm cryopreservation success depends upon the maintenance of spermatozoa fertility potential. Sperm cells must preserve both integrity and functionality of several cell structures. The stabilization phase must allow the exit of water from the sperm cells via osmosis. This study aimed to compare the effect of refrigeration in the commercial refrigerator (CR) and the transport/refrigeration box (TRB) upon the viability of frozen bull sperm diluted in three different extenders (A, B and C). Ten Nellore bulls, Bos taurus indicus maintained in Artificial Insemination Center were used and the spermatozoa samples was assessed for Plasma Membrane Integrity and CASA evaluation. The stabilization phase (5 degrees C/4 hours) was performed in the CR as well as in the TRB, and then samples were exposed to nitrogen vapor during 20 minutes and then plunged into nitrogen. The statistical analysis was done using the variance analysis and the significance level was set at 5%. In the CR the post-thawing parameters for PM and ALH were higher (p < 0.05) in the extender A (glicine egg-yolk) and extender B (glicine egg-free) when compared with extender C (TRIS egg-yolk). As for BCF, STR and LIN, the parameters were higher (p < 0.05) in extender B than in C. Samples that were stabilized in the TRB presented higher post-thawing parameters (p < 0.05) for PM and LIN in extender A and extender B when compared with C. BCF and STR parameters were higher (p < 0.05) in extemder B when compared with C. Extender B samples had higher (p < 0.05) PMI when stabilized in CR. The findings in this experiment enable us to say that both CR and TRB were effective in keeping the viability of post-thawing bull semen.

Chicken embryo related (CER) cell line for quantification of rabies neutralizing antibody by fluorescent focus inhibition test

Levels of rabies virus neutralization antibody in sera from vaccinated dogs and cattle were either measured by mouse neutralization test (MNT) or by rapid fluorescent focus inhibition test (RFFIT), performed on CER monolayers. The two tests were compared for their ability to detect the 0.5 International Units/ml (I.U.) recommended by the World Health Organization (WHO) as the minimum response for proof of rabies immunization. A significant correlation was found between the two tests (n = 211; r = 0.9949 in dogs and 0.9307 in cows, p < 0.001), good sensitivity (87.5%), specificity (94.7%) and agreement (96.6%) as well. RFFIT method standardized on CER cell system for neutralizing antibodies detection turns the diagnosis easier and less expensive, specially when a great number of samples must be tested from endemic areas as commonly found in Brazil. (c) 2005 the International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.

Origin of sensory and autonomic innervation of the rat temporomandibular joint: A retrograde axonal tracing study with the fluorescent dye fast blue

Previous studies that have used retrograde axonal tracers (horseradish peroxidase alone or conjugated with wheat germ agglutinin) have shown that the temporomandibular joint (TMJ) is supplied with nerve fibers originating mainly from the trigeminal ganglion, in addition to other sensory and sympathetic ganglia. The existence of nerve fibers in the TMJ originating from the trigeminal mesencephalic nucleus is unclear, and the possible innervation by parasympathetic nerve fibers has not been determined. In the present work, the retrograde axonal tracer, fast blue, was used to elucidate these questions and re-evaluated the literature data. The tracer was deposited in the supradiscal articular space of the rat TMJ, and an extensive morphometric analysis was performed of the labeled perikaryal profiles located in sensory and autonomic ganglia. This methodology permitted us to observe labeled small perikaryal profiles in the trigeminal ganglion, clustered mainly in the posterior-lateral region of the dorsal, medial and ventral thirds of horizontal sections, with some located in the anterior-lateral region of the ventral third. Sensory perikarya were also labeled in the dorsal root ganglia from C2 to C5. No labeled perikaryal profiles were found in the trigeminal mesencephalic nucleus. on the other hand, autonomic labeled perikaryal profiles were distributed in the sympathetic superior cervical and stellate ganglia, and parasympathetic otic ganglion. Our results confirmed those of previous studies and also demonstrated that: (i) there is a distribution pattern of labeled perikaryal profiles in the trigeminal ganglion; (ii) some perikaryal profiles located in the otic ganglion were labeled; and (iii) the trigeminal mesencephalic nucleus did not show any retrogradely labeled perikaryal profiles.

In vivo uptake of a haem analogue Zn protoporphyrin IX by the human malaria parasite P. falciparum-infected red blood cells

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Isolation and characterization of a satellite DNA family in Achirus lineatus (Teleostei : Pleuronectiformes : Achiridae)

Agarose gels stained with Ethidium bromide and Southern blot experiments of HindIII-digested genomic DNA of Achirus lineatus evidenced the presence of monomers and multimers of a DNA segment of about 200 bp, named here Al-HindIII sequence. No signals were observed in Southern blot experiments with genomic DNA of other flatfish species. The DNA sequencing of four recombinant clones showed that Al-HindIII sequences had 204 bp and were 63.72% AT-rich. FISH experiments using a Al-HindIII sequence as probe showed bright signals in the centromeric position of all chromosomes of A. lineatus.